feat: add Number of Ways to Select Buildings (#1140)

* add Number of Ways to Select Buildings

* Update 2222.c

add new line at the end

* Rename README.md to DIRECTORY.md

* Update leetcode/src/2222.c

Co-authored-by: Taj <tjgurwara99@users.noreply.github.com>

* fix review notes

Co-authored-by: David Leal <halfpacho@gmail.com>
Co-authored-by: Taj <tjgurwara99@users.noreply.github.com>

leetcode/DIRECTORY.md

@@ -112,5 +112,6 @@
 | 1752 | [Check if Array Is Sorted and Rotated](https://leetcode.com/problems/check-if-array-is-sorted-and-rotated/)                     | [C](./src/1752.c) | Easy       |
 | 2024 | [Maximize the Confusion of an Exam](https://leetcode.com/problems/maximize-the-confusion-of-an-exam/)                           | [C](./src/2024.c) | Medium     |
 | 2130 | [Maximum Twin Sum of a Linked List](https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/)                           | [C](./src/2130.c) | Medium     |
+| 2222 | [Number of Ways to Select Buildings](https://leetcode.com/problems/number-of-ways-to-select-buildings/)                         | [C](./src/2222.c) | Medium     |
 | 2270 | [Number of Ways to Split Array](https://leetcode.com/problems/number-of-ways-to-split-array/)                                   | [C](./src/2270.c) | Medium     |
 | 2304 | [Minimum Path Cost in a Grid](https://leetcode.com/problems/minimum-path-cost-in-a-grid/)                                       | [C](./src/2304.c) | Medium     |

leetcode/src/2222.c

@@ -0,0 +1,30 @@
+long numberOfWaysForChar(char * s, char c){
+    long firstBuildingAppearNumber = 0;
+    long secondBuildingAppearNumber = 0;
+    long result = 0;
+    
+    int sLength = strlen(s);
+    for (int i = 0; i < sLength; i++){
+        if (s[i] == c){
+            result += secondBuildingAppearNumber;
+
+            firstBuildingAppearNumber += 1;
+            continue;
+        }
+
+        secondBuildingAppearNumber += firstBuildingAppearNumber;
+    }
+    
+    return result;
+        
+}
+
+// numberOfWays returns the sum of number ways of selecting first building
+// and the number of ways of selecting second building which gives us the
+// number of ways of selecting three building such that no
+// consecutive buildings are in the same category.
+// Runtime: O(n)
+// Space: O(n)
+long long numberOfWays(char * s){
+    return numberOfWaysForChar(s, '0') + numberOfWaysForChar(s, '1');
+}